Not doing postback after some idle time

hello everyone,
i have a website which runs fine on my dev envirenment and local iis but on remote server when i leave website idle for 4-5 min or even if i use website for 4-5 min , after 4-5 min if  i do a post back from button etc. it displays error in application
this is my web.config file
<?xml version="1.0" encoding="UTF-8"?>
<!--
    Please refer to machine.config.comments for a description and
    the default values of each configuration section.

    For a full documentation of the schema please refer to
    http://go.microsoft.com/fwlink/?LinkId=42127

    To improve performance, machine.config should contain only those
    settings that differ from their defaults.
-->
<configuration>
 <connectionStrings>
    <add name="AddManagerDBConnectionStri ...